This study utilizes a unique opportunity to obtain samples from the home environment of children with acute lymphocytic leukemia (ALL) to assess exposure to a range of pesticides, polynuclear aromatic hydrocarbons (PAH), and metals. The subjects are a subset of those participating in a case- control interview study of ALL and a substudy of electromagnetic field exposures (EMF), now in progress, that involves visits by trained technicians to the homes of all ALL cases, diagnosed between 2/1/89 and 12/31/92, and their matched controls in the six-state region of Ohio, Pennsylvania, Michigan, Minnesota, Indiana and Illinois. For 250 cases and 250 controls who have lived in their current residence for at least three years, and/or for a substantial fraction of their life, samples of house dust will be collected. The dust will be examined (1) to determine the quantity of 25 pesticides, 6 PAHs and 8 metals in the sample, and (2) to estimate automobile traffic density in the neighborhood through use of signature compounds. The pesticides under study are those in common use in the home and those suspected to be carcinogenic. the data will be used to estimate relative risks for exposure to each compound, to correlate direct measures with data obtained at interview, and to assess the importance of these exposures as confounders for EMF exposure. Samples will also be stored for future use. The importance of this study is that it will provide a direct and unbiased means of assessing exposure to a large number of compounds, many suspected to be carcinogenic, that are common in the environment. Pesticides have been the subject of a great deal of public discussion in recent years, with particular concern over their potential to cause childhood ALL. The findings of this study, whether positive or negative, will have a significant impact in terms of public health policy and education.